The current bss clear logic assumes the target mmap address and host
address are the same.  Use g2h to translate from the target address
space to the host so we can call memset on it.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>